Hurricane Maria made landfall in Puerto Rico early on 20 September as a strong category 4 Hurricane, packing maximum sustained winds of 155 mph. The island received significant damage, including the loss of both radars (TSJU and TJUA). Given the vast devastation, WFO Miami was providing service backup for Puerto Rico. Without radar coverage over the island, forecasters needed to rely heavily on other datasets such as satellite imagery from GOES-16. To provide the best/most information possible, a GOES-16 1-min mesoscale sector was available continuously over Puerto Rico.  Having this sector was especially important because, from checkout position, the GOES-16 5-min CONUS sector coverage ends halfway across Puerto Rico (Fig 1). Outside of that sector, coverage is 15-min.

Figure 2: 30 September 2017 GOES-16 1-min VIS/IR sandwich image combination. Full res:

On 30 September, a tropical wave interacting with an upper-level trough was producing strong thunderstorms near Puerto Rico. Given the expected heavy rain and already saturated soils, a flash flood watch was issued for the island. During the morning, strong thunderstorms were oriented just south of the island. The appearance of these storms in satellite imagery led to the issuance of a Special Marine Warning per warning text (SOURCE…SATELLITE IMAGERY INDICATED). The 1-min GOES-16 IR/VIS sandwich image combo shows the burst of thunderstorms and warning product.

Figure 2: 30 September 2017 GOES-16 1-min VIS/IR sandwich image combination. Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/20170920_pr_1min1.gif

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

In May, it was announced that GOES-16 would become GOES-East late in the calendar year. This week, detailed drift plans were released!

• GOES-16 will begin drifting from the checkout position (89.5W) on 30 November, reaching the GOES-East position (75.2W) on 11 December. After a period of calibration, the satellite will return to operations as GOES-East on 14 December.
• GOES-16 ABI, GLM, SUVI, SEISS, and EXIS data will not be available between 30 Nov and 14 Dec.
• GOES-13 (current GOES-East) will remain at 75W until 2 January, when it will begin drifting to its storage location at 60W. It will reach the storage location on 22 January.

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

On 11 September 2017, the NWS Pueblo WSR-88D radar (KPUX) was taken down for emergency repairs. KPUX would not come back online until 24 September. While the Denver radar (KFTG) could be used by Pueblo forecasters during the outage, the loss of KPUX meant significantly reduced radar coverage for southern Colorado. Radar coverage is poor to begin with in the western part of the Pueblo CWA (mountains and mountain valleys) due to radar beam blockage. To help compensate, NWS Pueblo requested GOES-16 1-min mesoscale sectors when high impact weather threatened the region.

KFTG failed on 23 September, a day on which widespread heavy rainfall and strong-severe thunderstorms were expected across southern Colorado, and would not return to service until later that evening (0300 UTC). With both KPUX and KFTG out, NWS Pueblo forecasters were left using radars such as CYS and GLD, whose lowest beams scan roughly 20,000 ft AGL over Pueblo and Colorado Springs. NWS Pueblo requested a 1-min mesoscale sector, but was denied due to coverage over Puerto Rico (ongoing cleanup efforts from Maria with their radar down) and ongoing Hurricane Maria. Maria was out at sea with no TC Watches or Warning in effect, so it is unclear at the time of this writing why that sector was not moved over Colorado.

On 23 September, therefore, NWS Pueblo forecasters relied heavily on GOES-16 imagery (5-min), lightning data, and ground truth. One severe thunderstorm warning was issued for a storm in far eastern Colorado, where KGLD provided adequate information. The greatest forecast challenge for PUB existed over the southeast mountains and adjacent plains, where periods of heavy rainfall went undetected by radar. With shallow warm rain processes dominant, the precip was oriented below the lowest available radar beams. Two flood advisories were issued by PUB during the evening. The radar composite animation below demonstrates coverage over Colorado from 2300 UTC – 0400 UTC, during which both KPUX and KFTG were down (Fig. 1). The majority of the Pueblo forecast area was without coverage. The return of KFTG can be seen at 0300 UTC.

Figure 1: 2300 UTC – 0400 UTC 23-24 September 2017 1 km radar composite imagery. NWS/PUB flood advisories overlaid. Full res

Reference figure 2 during discussion in the next two paragraphs. The first flood advisory was issued at 0027 UTC (24 Sep) for much of the Colorado Springs area. Abundant rain gauges, satellite imagery, lightning data, and spotter reports provided the information needed to issue the advisory. Prior to reports of heavy rain in Colorado Springs, heavy rain was reported in the more rural town of Pueblo West to the south. As the clouds associated with this rainfall streamed north, they cooled considerably, indicating to the forecaster that it was plausible Colorado Springs would receive rainfall at least to the degree of that being reported to the south. Nearby lightning strikes also indicated potential for localized heavy rainfall. Reports of heavy rainfall in Springs began to come in as the cooling clouds moved over the urban area, and along with the continued streaming of cooling clouds from the south, provided confidence to issue a flood advisory. Minor street and stream flooding was reported throughout the city along with one water rescue from Fountain Creek.

The second flood advisory was issued at 0149 UTC over the Junkins Burn Scar, located in the Wet Mountains southwest of Pueblo. Previous posts on this blog have referenced the Junkins burn scar, which is the result of an October 2016 Wildfire. Burn scars pose a significant flash flood risk given the lack of debris and less porous nature of the land surface. There aren’t any rain gauges on the burn scar and spotters are scarce in the area, forcing the forecaster to rely even more on GOES-16 IR data. Cold cloud tops detected in GOES-16 5-min IR imagery were analyzed heading towards the burn scar. The forecaster on shift compared these cloud top temperatures with those associated with the heavy rain that was confirmed to have occurred in the Pueblo West and Colorado Springs areas. Given the similarities (clouds over Junkins just slightly warmer than those over Colorado Springs, but cooler than those over Pueblo West), the local sheriff’s departments were notified of the potential flood threat and a flood advisory was issued. Thankfully, there were no reports of flooding over or near the burn scar, but it is unclear whether or not moderate-heavy rainfall occurred.

Figure 2: 2300 UTC – 0400 UTC 23-24 September 2017 GOES-16 5-min IR imagery. NWS/PUB flood advisories overlaid. Full res

This event exemplifies the increased value of rapidly updating satellite imagery under unique circumstances such as radar outages.

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

Severe storms developed across the Dakota’s ahead of and along a cold front in association with a potent shortwave on 19 September 2017. An SPC Enhanced risk was issued for tornadoes, significant hail, and significant wind. Given the threat, WFO Bismark requested and was granted a 1-min meso sector. Meanwhile, Hurricane Maria continued to advanced to the Northwest through the Atlantic toward Puerto Rico. The other meso sector was positioned over Hurricane Maria as requested by the National Hurricane Center. These two meso requests represent two of the top four priorities on the meso sector priority list in the event of multiple requests. Meso requests for SPC Enhanced risk is the number three priority, while meso requests for hurricane warnings over the US and its territories is number four. Only an SPC high/moderate risk (number one) or a Volcanic eruption affecting the US and its territories (number two) have higher priority.

Figure 1: 2045 UTC – 2144 UTC 19 September 2017 GOES-16 1-min imagery for severe thunderstorm over North Dakota (left) and Hurricane Maria (right). Full res: https://satelliteliaisonblog.files.wordpress.com/2017/09/201700919_2p_vis_maria_severe2_anno.gif

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”